[RFC] regmap: Add regmap_field APIs

[Srinivas KANDAGATLA]

From: Srinivas Kandagatla <srinivas.kandagatla@xxxxxx>

It is common to access regmap registers at bit level, using
regmap_update_bits or regmap_read functions, however the end user has to
take care of a mask or shifting. This becomes overhead when such use
cases are high. Having a common function to do this is much convient and less
error prone.

The idea of regmap_field is simple, regmap_field gives a logical structure to
bits of the regmap register, and the driver can use this logical entity without
the knowledge of the bit postions and masks all over the code. This way code
looks much neat and it need not handle the masks, shifts every time it access
the those entities.

With this new regmap_field_read/write apis the end user can setup a
regmap field using regmap_field_init and use the return regmap_field to
read write the register field without worrying about the masks or
shifts.
Also this apis will be usefull for drivers which are based on regmaps,
like some clocks or pinctrls which can work on the regmap_fields
directly without having to worry about bit positions.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxx>
---
Hi Mark,

I have been looking at using regmap mmio directly for ST "System Configuration
registers". One thing which we discussed 2 weeks back in syscon patch was, if
this new functionality would benifit others. Having thought about it, I think
that if regmap had a concept like regmap_field we would have used it straight way
without a new driver.

I generated this patch mainly to get your opinion on these new APIs, Is this the
right place for these APIs, or do you suggest that these APIs should go in SOC
Specific driver?

Comments?

Thanks,
srini



 drivers/base/regmap/regmap.c |   47 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/regmap.h       |   28 +++++++++++++++++++++++++
 2 files changed, 75 insertions(+), 0 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index a941dcf..4512df7 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1249,6 +1249,27 @@ int regmap_raw_write(struct regmap *map, unsigned int reg,
 }
 EXPORT_SYMBOL_GPL(regmap_raw_write);
 
+/**
+ * regmap_field_write(): Write a value to a single register field
+ *
+ * @field: Register field to write to
+ * @val: Value to be written
+ *
+ * A value of zero will be returned on success, a negative errno will
+ * be returned in error cases.
+ */
+
+int regmap_field_write(struct regmap_field *field, unsigned int val)
+{
+	int field_bits;
+	unsigned int reg_mask;
+	field_bits = field->msb - field->lsb + 1;
+	reg_mask = ((BIT(field_bits) - 1) << field->lsb);
+	return regmap_update_bits(field->regmap, field->reg,
+				reg_mask, val << field->lsb);
+}
+EXPORT_SYMBOL_GPL(regmap_field_write);
+
 /*
  * regmap_bulk_write(): Write multiple registers to the device
  *
@@ -1532,6 +1553,32 @@ int regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
 EXPORT_SYMBOL_GPL(regmap_raw_read);
 
 /**
+ * regmap_field_read(): Read a value to a single register field
+ *
+ * @field: Register field to read from
+ * @val: Pointer to store read value
+ *
+ * A value of zero will be returned on success, a negative errno will
+ * be returned in error cases.
+ */
+
+int regmap_field_read(struct regmap_field *field, unsigned int *val)
+{
+	int field_bits;
+	int ret;
+	ret = regmap_read(field->regmap, field->reg, val);
+	if (ret != 0)
+		return ret;
+
+	field_bits = field->msb - field->lsb + 1;
+	*val >>= field->lsb;
+	*val &= (BIT(field_bits) - 1);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(regmap_field_read);
+
+/**
  * regmap_bulk_read(): Read multiple registers from the device
  *
  * @map: Register map to write to
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 02d84e2..f8dba11 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -411,6 +411,34 @@ bool regmap_reg_in_ranges(unsigned int reg,
 			  const struct regmap_range *ranges,
 			  unsigned int nranges);
 
+struct regmap_field {
+	struct regmap *regmap;
+	unsigned int reg;
+	unsigned int lsb;
+	unsigned int msb;
+};
+
+#define REGMAP_FIELD_INIT(regmap, reg, lsb, msb) { 	\
+				.regmap = regmap, 	\
+				.reg = reg, 		\
+				.lsb = lsb, 		\
+				.msb = msb, 		\
+			}
+
+/* dynamic version of regmap_field intialization */
+static inline void regmap_field_init(struct regmap_field *field,
+	struct regmap *regmap,	unsigned int reg,
+	unsigned int lsb, unsigned int msb)
+{
+	field->regmap = regmap;
+	field->reg = reg;
+	field->lsb = lsb;
+	field->msb = msb;
+}
+
+int regmap_field_read(struct regmap_field *field, unsigned int *val);
+int regmap_field_write(struct regmap_field *field, unsigned int val);
+
 /**
  * Description of an IRQ for the generic regmap irq_chip.
  *
-- 
1.7.6.5

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